Dried egg albumen is a well known commercial product. Albumen, after separation from yolk, is subjected to a desugaring step to avoid browning upon drying. Desugaring is generally accomplished by treating egg albumen with bacteria such as Enterobacter Aerogenes which consume the glucose in the egg. The desugared egg albumen is then dried such as by pan drying or spray drying. The details are more fully set forth in the Science and Technology of Egg Products Manufactured in the United States, Forsythe R. (1968) (publisher).
Since it is well known that egg albumen is a perfect breeding ground for various bacteria including the highly toxic salmonella, the product must be pasteurized before distribution and sale. One of the effective pasteurization means is termed "Hot Room Treatment". In this treatment the dried egg albumen in closed containers is placed in a clean sealed room, the containers being spaced sufficiently to assure adequate heat penetration and air circulation. Spray dried albumen is heated throughout to a temperature of not less than 130.degree. F. and held continuously at such temperature for not less than five days and until it is salmonella negative. Pan dried albumen is heated throughout to a temperature of not less than 125.degree. F. and held continuously at such temperature for not less than five days and until salmonella negative. This is set forth in the U.S. Department of Agriculture regulations governing the inspection of eggs and egg products (7 CFR 59.575). An average treatment time is two weeks.
Much experimental work has been conducted to determine the effect of this type of pasteurization on the content of salmonella and the functional properties of the egg albumen. In the article entitled "The Effect of High-Temperature Storage on the Content of Salmonella and on the Functional Properties of Dried Egg White" by G. J. Banwart and J. C. Ayres, Food Technology 10:68-73, it is indicated that albumen containing 1.5, 3 or 6% moisture stored for 150, 120 and 90 days respectively at 50.degree. C. provided good salmonella control without any significant loss in the volume of angel cakes. Albumen with 12% moisture showed a significant decrease in the volume of resulting angel cakes when stored for three days. Of similar import are the papers entitled "High Temperature Storage of Spray-Dried Egg White", No. 1, Whipping Time and Quality of Angel Cake, by R. E. Baldwin et al., Poultry Science 46:1421-1430; "High Temperature Storage of Spray-Dried Egg White", No. 2, Electrophoretic Mobility, Conalbumen-Iron Complexing, Sulfhydryl Activity, and Evolution of Volatile Bases, by O. J. Cotterill, Poultry Science 46:1431-1437; "Spray Drying of Egg White at Various pH Levels" by W. M. Hill, Poultry Science 44:1155-1163 and "High Temperature Storage of Spray-Dried Egg White" by L. E. McBee et al., Poultry Science: 50, No. 2 pages 452-458.
It is also well known to prepare various products from whey, the by-product of cheese manufacture. The products that can be obtained from whey include, among others, a whey protein concentrate. Whey protein concentrates can be made by numerous methods including gel fractionation (U.S. Pat. No. Re. 27,806) as well as by ultrafiltration. An illustrative method for ultrafiltration is described by Horton, B. S. et al., Food Technology, Volume 26, page 30 (1972). Whey protein concentrate generally has about 35% to about 80% protein. One of the proteins in the whey protein concentrate is a water soluble protein of the albumenoid class of proteins. Because some of the protein in whey protein concentrate is from the same class as that of egg albumen, workers thought that one of the obvious areas of use of this lower cost protein would be in extending egg albumen. Various workers have attempted to substitute whey protein concentrate for egg albumen in various recipes. Depending on the functionality for which the eggs were used, the richness in eggs of the recipe and the type of whey protein concentrate used, sucesses have been sporadic. In attempting to make a hard-whipped meringue, whey protein concentrate from ultrafiltration is not entirely satisfactory. In general, the critical test for the substitution is the preparation of angel cake and it is not known whether or not any whey protein can be used as a substitute for egg albumen whether alone or partially (around 50%). Various prior processes for preparing "egg white substitutes" are disclosed in the prior art discussion in U.S. Pat. No. 4,089,987. In general, the replacements on a functional basis cannot be accomplished without the addition of secondary ingredients such as carboxymethylcellulose or the materials disclosed in U.S. Pat. No. 4,089,987. In the past blends of egg albumen and whey protein concentrate have been made in a recipe by partially replacing egg albumen. This is generally accomplished using either liquid or dried egg albumen and a whey protein concentrate.
One of the unique properties of egg albumen is its ability to form a stable gel at a relatively low temperature. A 15% solution of a desugared spray-dried egg albumen which has been hot room treated as standard in the industry will provide a gel by heating the solution to a temperature of about 70.degree. C. for about 30 minutes. It is also possible to gel a whey protein concentrate by heating a solution of 15% whey protein for 30 minutes at 85.degree. C. Relative gel strengths for the respective products are about 90 grams and 450 grams respectively as tested with a penetrometer. In attempting to provide blends of egg albumen and whey protein concentrate for use as gel forming material, it was discovered that the gels provided by the blends are weaker than that provided by the weakest component used alone. The same result is achieved when the whey protein concentrate is mixed with the egg and then hot room treated or if the whey protein concentrate is hot room treated prior to it mixing with the spray-dried egg white. In both cases the product would brown and be unacceptable. These findings severely limit the use of whey protein concentrate as a blend with egg albumen in areas where the gelling function of the egg albumen is of significance.